1. Field of the Invention
The present invention relates to an optical disk that forms a recording mark having a different physical characteristic from that of the other portion on a recording medium to store information and an optical disk device that reads information from the medium.
2. Description of the Related Art
The optical disk medium includes various types such as a CD-R/RW, DVD-RAM, DVD±R/RW, Blu-ray Disc (hereinafter referred to as BD), HD DVD, and the like, and such an optical disk medium that includes one with two data layers has come into general use. A so-called DVD super multi-drive, which is provided for writing/reading on/from CD-R/RW, DVD-RAM and DVD±R/RW, has widely available as the corresponding optical disk device. It is expected that high-performance drives, which are provided for BD and HD DVD, will be widely available in the future.
Today, a super-resolution technique, a solid immersion lens (SIL) and the like for next-generation large-capacity optical disks are proposed. A certain super-resolution technique is described, for example, in Japanese application JP 2006-107588. This describes that a phase-change recording film, which changes its optical characteristics when it melts, is embedded in pits to thereby perform super-resolution reading. Concurrently, recording marks are spatially separated from each other so as to reduce thermal interference between the recording marks and jitter in a super-resolution region. The aforementioned configuration makes it possible to improve linear density and track density at the same time, and as a result, storage capacity of the optical disk can be largely increased. Further, light transmittance in the region between data pits is increased to thereby allow an increase in an average light transmittance, so that high light utilization efficiency is achieved to produce an advantage for a multi-layering process. This type is hereinafter called as a three-dimensional pit selection type. As a means for embedding the recording film in the pit, it is possible to use a phase-change etching method (method using a difference in etching speed between liquid crystal and amorphous) and a physical polishing method such as a chemical mechanical polishing (CMP) as described in Japanese application JP 2005-100526.